JPWO2017135080A1 - Pulse arc welding control method and pulse arc welding apparatus - Google Patents

Abstract

The welding current is fed at the feed speed while the welding current is supplied to the welding wire by alternately repeating the peak current period in which the welding current is a peak current and the base current period in which the welding current is smaller than the peak current. The pulse arc welding apparatus is controlled so as to weld the workpiece by generating an arc between the welding wire and the workpiece to be fed. In order to keep the arc length of the arc constant, the feed speed is set to the first feed speed during the base current period, and the feed speed is larger than the first feed speed and the first feed speed during the peak current period. Is set to the second feeding speed according to. By this method, good welding quality with reduced spatter and undercut can be obtained.

Description

  The present invention relates to a pulse arc welding control method and a pulse arc welding apparatus for performing pulse arc welding while feeding a welding wire which is a consumable electrode.

  In conventional pulse arc welding, when high-speed welding by mild steel pulse MAG welding is performed, the undercut that remains as a groove without being sufficiently filled with molten metal is dug into the work piece. Therefore, it is a general construction pattern to perform welding while lowering the welding voltage to shorten the arc length and shifting the droplet to a short circuit. However, at the time of short circuit, the short circuit current is increased from the start of the short circuit until the short circuit is opened with a predetermined slope. Thereby, when the short circuit is opened, the short circuit current may reach a high value of 200 to 300 A, and when the short circuit is opened, spatter may occur.

  In order to suppress the occurrence of spatter, in the process of increasing the short-circuit current with a predetermined slope from the start of short-circuiting at the time of short-circuiting, if a necking is detected immediately before opening the short-circuit, the short-circuit current is sharply reduced to a low value A pulsed arc welding method is known (see, for example, Patent Document 1).

  FIG. 9 shows a waveform of the welding current I when a short circuit occurs in conventional pulse arc welding. In this method, constriction (neck) control is performed, and the welding current I is sharply reduced.

  When a short circuit occurs during pulse welding, a current with a slope smaller than the slope at the rise of the pulse current is applied to open the short circuit, and the necking is detected when the short circuit is released due to this conduction, and welding is performed. Reduce current sharply. Therefore, it is possible to reduce the influence of the welding current on the occurrence of spatter when the short circuit is opened, and as a result, it is possible to reduce the amount of spatter generated when the short circuit is opened.

JP 2006-334601 A

  The welding current is fed at the feed speed while the welding current is supplied to the welding wire by alternately repeating the peak current period in which the welding current is a peak current and the base current period in which the welding current is smaller than the peak current. The pulse arc welding apparatus is controlled so as to weld the workpiece by generating an arc between the welding wire and the workpiece to be fed. In order to keep the arc length of the arc constant, the feed speed is set to the first feed speed during the base current period, and the feed speed is larger than the first feed speed and the first feed speed during the peak current period. Is set to the second feeding speed according to.

  By this method, good welding quality with reduced spatter and undercut can be obtained.

FIG. 1 is a schematic configuration diagram of a pulse arc welding apparatus according to the first embodiment. FIG. 2 is a diagram showing a welding current, a welding voltage, a welding wire feed speed, and a state of droplet transfer in the operation of the pulse arc welding apparatus in the first embodiment. FIG. 3 is a diagram showing a welding current, a welding voltage, a feeding speed, and a state of droplet transfer in the operation of the pulse arc welding apparatus of the comparative example. FIG. 4 is a diagram showing a welding current, a welding voltage, a feeding speed, and a state of droplet transfer in another operation of the other pulse arc welding apparatus in the first embodiment. FIG. 5 is a diagram showing the feed rate of the welding wire of the pulse arc welding apparatus in the first embodiment. FIG. 6 is a diagram showing a schematic configuration of the pulse arc welding apparatus in the second embodiment. FIG. 7A is a diagram showing a welding current, a welding voltage, and a welding wire feeding speed droplet transfer state in the operation of the pulse arc welding apparatus in the second embodiment. FIG. 7B is an enlarged view of the feeding speed shown in FIG. 7A. FIG. 8 is a diagram showing the feed speed of the welding wire of the pulse arc welding apparatus in the second embodiment. FIG. 9 is a diagram showing a welding current in conventional pulse arc welding.

(Embodiment 1)
FIG. 1 is a schematic configuration diagram of a pulse arc welding apparatus 1001 according to the first embodiment. The pulse arc welding apparatus 1001 mainly includes a welding power supply device 18 called a welding machine and a robot 21 called a manipulator.

  The welding power supply device 18 includes a welding power supply unit 18a that outputs a welding output including a welding current I and a welding voltage V, and a welding control unit 18b that controls the welding power supply unit 18a. The welding power source device 18 includes a primary rectification unit 2 that rectifies the output of the input power source 1, a switching element 3 that controls the welding output by controlling the output of the primary rectification unit 2, and power from the switching element 3. Transformer 4 that performs insulation conversion, secondary rectification unit 5 that rectifies the secondary output of transformer 4, reactor 6 (also referred to as DCL) connected in series to secondary rectification unit 5, and switching element 3 And an output control unit 7 for driving. The welding power supply device 18 includes a welding voltage detection unit 8 that detects the welding voltage V, a welding current detection unit 9 that detects the welding current I, and an output of the welding voltage detection unit 8 and / or an output of the welding current detection unit 9. A short-circuit / arc detection unit 10 for determining whether the welding state is a short-circuit state or an arc state, a short-circuit control unit 11 for controlling the output control unit 7 during the short-circuit period, and an output control unit during the arc period 7 is further provided. The welding power supply device 18 further includes a wire feed control unit 17, an output terminal 29a, and an output terminal 29b.

  The arc control unit 12 includes a pulse waveform control unit 13 including a pulse rising control unit 14, a peak current control unit 15, and a pulse falling control unit 16.

  The robot control unit 19 that controls the operation of the robot 21 includes a welding condition setting unit 20 for setting welding conditions. The robot controller 19 is communicably connected to the welding power supply device 18. Note that a torch 26 is attached to the robot 21.

  A welding condition setting unit 20 inside the robot control unit 19 connected to the welding power source device 18 is for setting a welding current, a welding voltage, and the like. The output terminal 29 a of the welding power supply device 18 is electrically connected to the tip 27 that holds the welding wire 23 in the torch 26, and power is supplied to the welding wire 23 via the tip 27. The output terminal 29 b of the welding power supply device 18 is electrically connected to the workpiece 24 and supplies power to the workpiece 24. An arc 28 is generated between the tip of the welding wire 23 and the workpiece 24. A wire feeding unit 25 including a feeding roller feeds the welding wire 23 toward the workpiece 24 at a feeding speed WF from the welding wire storage unit 22 that stores the welding wire 23 toward the tip 27. .

  In addition, each component part which comprises the pulse arc welding apparatus 1001 shown in FIG. 1 may each be comprised independently, and you may make it comprise combining a some component part.

  FIG. 2 shows the welding current I, welding voltage V, feed speed WF, and droplet transfer state of the pulse arc welding apparatus 1001. The welding power source 18 supplies a welding voltage V and a welding current I to the welding wire 23 to generate an arc 28 between the welding wire 23 and the workpiece 24 and melt the welding wire 23 to weld the welding wire. A droplet 23 d is formed at the tip of 23. The droplet 23d moves from the tip of the welding wire 23 to the workpiece 24 and adheres, and the workpiece 24 is welded. The pulse arc welding apparatus 1001 is configured to keep the arc length H of the short arc 28 constant so that the welding wire 23 and the workpiece 24 are not short-circuited in the droplet transfer (detachment) state. When the droplet 23 d is formed at the tip of the welding wire 23 and connected to the welding wire 23, the arc 28 is generated between the droplet 23 d formed at the tip of the welding wire 23 and the workpiece 24. . Therefore, when the droplet 23d is formed at the tip of the welding wire 23 and connected to the welding wire 23, the arc length H of the arc 28 is substantially equal to the droplet 23d formed at the tip of the welding wire 23. This is the distance to the work piece 24. When the droplet 23d is not formed at the tip of the welding wire 23 or when the droplet 23d is not connected to the tip of the welding wire 23, the arc 28 is generated between the tip of the welding wire 23 and the workpiece 24. To do. That is, when the droplet 23d is not formed at the tip of the welding wire 23 or when the droplet 23d is not connected to the tip of the welding wire 23, the arc length H of the arc 28 is substantially equal to the tip of the welding wire 23. This is the distance to the work piece 24. The welding current I shown in FIG. 2 alternately repeats a peak current period IPT in which the welding current I is the peak current IP and a base current period IBT in which the welding current I is a base current IB smaller than the peak current IP.

  In the pulse arc welding apparatus 1001 shown in FIG. 2, the welding current I, the welding voltage V, the state of droplet transfer, and the feeding speed WF, the feeding speed WF is increased in the peak current period IPT for growing the droplet 23d, By realizing a stable droplet transfer (detachment) state in the base current period IBT, a change in the arc length H is suppressed and the arc length H is kept at a constant value H1.

  FIG. 3 shows the welding current I, welding voltage V, droplet transfer state, and feed speed WF of the pulse arc welding apparatus of the comparative example. In the pulse arc welding apparatus of the comparative example, the feeding speed WF of the welding wire 23 is constant and the droplets are transferred (detached) in the base current period IBT. Thereby, the arc length H changes in the range from the value H1 to the value H2.

  The pulse waveform of the welding current I shown in FIG. 3 is a basic pulse waveform that realizes stable droplet transfer (detachment) that is repeated periodically in a steady welding period. The pulse waveform of the welding current I includes a pulse rising period IPRT in which the welding current I transitions from the base current IB to the peak current IP, a peak current period IPT in which the welding current I is the peak current IP, and a welding current I that is the peak current IP. Includes a pulse falling period IPFT in which a transition is made from the base current IB to a base current IB and a base current period IBT in which the welding current I is the base current IB. By periodically repeating the pulse rising period IPRT, the peak current period IPT, the pulse falling period IPFT, and the base current period IBT at the pulse frequency PHz, a periodic droplet transfer state is obtained.

  In the droplet transfer shown in FIG. 2 and FIG. 3, the welding control unit 18b causes the peak current IP, the base current IB, and the pulse rising period so as to realize one pulse and one drop in which the droplet 23d is detached once per pulse. The pulse waveform parameters for determining the pulse waveforms such as IPRT, peak current period IPT, pulse falling period IPFT, base current period IBT, etc. are adjusted. The pulse waveform parameter varies depending on the welding conditions of the work piece 24, the welding wire 23 to be used, and the like, and can be obtained in advance, for example, by confirmation of construction such as an experiment.

  The welding current I, welding voltage V, droplet transfer state, and feeding speed WF of the pulse arc welding apparatus of the comparative example shown in FIG. 3 will be described in detail. The welding control unit of the pulse arc welding apparatus of the comparative example starts the transition of the welding current I from the base current IB to the peak current IP at the time t1 when the pulse rising period IPRT starts, and the welding current I at the time t2 when the pulse rising period IPRT ends. To reach the peak current IP to start the peak current period IPT. The welding controller maintains the welding current I substantially at the peak current IP in the peak current period IPT. Thereafter, the welding control unit starts decreasing the welding current I from the peak current IP at the time t3 when the peak current period IPT ends, starts the pulse falling period IPFT, and sets the welding current I at the time t4 when the pulse falling period IPFT ends. The base current period IBT is started by reaching the base current IB smaller than the peak current IP. The welding control unit maintains the welding current I substantially at the base current IB in the base current period IBT. The welding control unit starts transition of the welding current I from the base current IB to the peak current IP at time t1 when the base current period IBT ends and the pulse rising period IPRT starts. In this manner, the welding control unit repeats the pulse rising period IPRT, the peak current period IPT, the pulse falling period IPFT, and the base current IB at the pulse frequency PHz (pulse period (1 / PHz)). The droplet 23d starts to grow in the pulse rising period IPRT in which the welding current I transitions from the base current IB to the peak current IP (state Sa), and the droplet 23d is in the peak current period IPT in which the welding current I is the peak current IP. It grows until it has the optimum size (state Sb). Thereafter, the droplet 23d connected to the welding wire 23 just before the droplet 23d is detached from the welding wire 23 at the tip of the welding wire 23 in the pulse falling period IPFT in which the welding current I transits from the peak current IP to the base current IB. And a welding wire 23 to form a constriction that forms a constriction that is a portion having a locally small diameter (state Sc). Thereafter, in the base current period IBT in which the welding current I is the base current IB, the droplet 23d is detached from the welding wire 23 (state Sd). Here, in the base current period IBT, after the droplet 23d is released (state Sd), the droplet 23d slightly grows and becomes larger due to the residual heat at the tip of the welding wire 23.

  In the pulse arc welding apparatus of the comparative example shown in FIG. 3, the feeding speed WF of the welding wire 23 is a constant feeding speed WF1 corresponding to the set current of the welding current I.

  By repeating this droplet transfer (detachment) state at the pulse frequency PHz, a stable welding state can be realized, and a bead with a beautiful appearance with less spatter can be realized.

  In the pulse arc welding apparatus of the comparative example shown in FIG. 3, the arc length H varies between different values H1 and H2 in the peak current period IPT and the base current period IBT. In the peak current period IPT, a large peak current IP is applied to the welding wire 23, the melting speed at which the welding wire 23 is melted becomes larger than the feeding speed WF1, and the arc length H is increased by forming the droplet 23d. (Value H2). In the base current period IBT, a small base current IB is applied to the welding wire 23, the melting speed of the welding wire 23 becomes smaller than the feeding speed WF1, and the arc length H becomes short (value H1).

  Thus, the arc length H changes between the value H1 and the value H2 in one cycle of the pulse waveform, and the change is repeated at the pulse frequency PHz. The molten droplet 23d forms a molten pool on the workpiece 24 until it moves onto the workpiece 24 and solidifies. The molten pool is made of a molten metal including a melted portion of the work piece 24. Even in the peak current period IPT, the molten pool becomes larger by temporarily increasing the arc length H to the value H2. A bead is formed in the workpiece 24 as the molten pool solidifies. The molten metal that becomes the bead begins to solidify from the edge of the cold bead, and the center of the hot bead finally solidifies as the final solidification point. When the work piece 24 is moved in the moving direction relative to the torch 26, the bead is elongated in the moving direction, and the final solidification point is the center in the width direction perpendicular to the moving direction of the bead. Therefore, the molten metal at the time of forming the bead solidifies so as to be pulled to the final freezing point. Therefore, as the distance between the edge of the bead having the lower temperature and the center of the bead having the higher temperature is larger, that is, the molten pool is larger, the amount of the molten metal at the edge of the bead tends to be insufficient.

  In the pulse arc welding apparatus of the comparative example, the undercut can be suppressed by reducing the welding voltage V to shorten the arc length H and the molten pool. However, the spatter due to the short-circuit between the welding wire 23 and the workpiece 24 may increase due to the drop 23d changing from the spray transfer to the short-circuit transfer due to the decrease in the welding voltage V.

  In the operation shown in FIG. 2 in the pulse arc welding apparatus 1001 according to the first embodiment, the work piece 24 is maintained while keeping the short arc length H constant so that the molten pool is small and a short circuit is not generated even during high-speed welding. Can be welded. This operation will be described below. The short arc length H that does not cause a short circuit is, for example, about 2 mm to 3 mm.

  In the pulse waveform of the welding current I shown in FIG. 2, the droplet 23d begins to grow in the pulse rising period IPRT in which the welding current I transitions from the base current IB to the peak current IP, similarly to the pulse waveform shown in FIG. 3 (state Sa point). Thereafter, the droplet 23d is grown to have an optimum size in the peak current period IPT in which the welding current I is the peak current IP (state Sb). Thereafter, a constricted state in which a constriction is formed, which is a state immediately before the droplet 23d is detached from the welding wire 23 at the tip of the welding wire 23 in the pulse falling period IPFT in which the welding current I transitions from the peak current IP to the base current IB. (State Sc) is generated. Thereafter, the droplet 23d is detached from the welding wire 23 in the base current period IBT in which the welding current I is the base current IB (state Sd).

  The operation shown in FIG. 2 differs from the operation of the comparative example shown in FIG. 3 in the feeding speed WF for feeding the welding wire 23. The welding control unit 18b sets the feeding speed WF to the feeding speed WF1. The welding control unit 18b starts to increase the feed speed WF toward the feed speed WF2 larger than the feed speed WF1 at the time t1 when the pulse rising period IPRT starts to reach the feed speed WF2. In the operation shown in FIG. 2, the welding current I reaches the feeding speed WF2 immediately after starting to increase from the feeding speed WF1 at time t1. Thereafter, the welding control unit 18b starts to decrease the feed speed WF from the feed speed WF2 in the peak current period IPT toward the feed speed WF1 in the base current period IBT at the time t3 when the pulse falling period IPFT starts. The feed speed WF1 is reached. In the operation shown in FIG. 2, the welding current I reaches the feeding speed WF1 immediately after starting to decrease from the feeding speed WF2 at time t3.

  The welding control unit 18b realizes a droplet transfer (detachment) state while periodically changing the feeding speed WF to the feeding speeds WF1 and WF2 at the pulse frequency PHz according to the pulse waveform of the welding current I. Thereby, a stable welding state can be realized while keeping the short arc length H constant, and a bead having a beautiful appearance with less spatter and no undercut can be formed.

  FIG. 4 shows a welding current I, a welding voltage V, a feeding speed WF, and a droplet transfer state in another operation of the pulse arc welding apparatus 1001 for making the arc length H constant. In FIG. 4, the same reference numerals are given to the same parts as those shown in FIG. In the operation shown in FIG. 4, the welding control unit 18b starts increasing the feeding speed WF of the welding wire 23 from the feeding speed WF1 to the feeding speed WF2 with a predetermined slope at the time t1 when the pulse rising period IPRT starts. The feed speed WF2 is reached after time t1, and then the feed speed WF2 is maintained. Thereafter, the welding control unit 18b starts to decrease the feeding speed WF from the feeding speed WF2 toward the feeding speed WF1 with a predetermined inclination at the time t3 when the peak current period IPT ends and the pulse falling period IPFT starts. After t3, the feed speed WF1 is reached at time t4 and then maintained at the feed speed WF1.

  As shown in FIG. 4, the welding control unit 18b starts to increase the feed speed WF from the feed speed WF1 toward the feed speed WF2 at a predetermined gradient at time t1, and reaches the feed speed WF2 at time t2. After that, it is preferable to maintain the feeding speed WF2. That is, a predetermined period in which the feed speed WF increases from the feed speed WF1 to the feed speed WF2 so that the period during which the feed speed WF increases from the feed speed WF1 to the feed speed WF2 coincides with the pulse rising period IPRT. It is preferable to adjust the inclination. Further, the welding control unit 18b starts to decrease the feeding speed WF from the feeding speed WF2 toward the feeding speed WF1 at a predetermined inclination at time t3, and after reaching the feeding speed WF1 at time t4, the feeding speed. It is preferable to maintain WF1. That is, a predetermined period in which the feeding speed WF decreases from the feeding speed WF2 to the feeding speed WF1 so that the period during which the feeding speed WF decreases from the feeding speed WF2 to the feeding speed WF1 coincides with the pulse falling period IPFT. It is preferable to adjust the inclination.

FIG. 5 shows the feeding speed WF2 of the feeding speed WF. Specifically, FIG. 5 shows a pulse MAG welding (Ar) using a shield gas 24G (see FIG. 1) in which the welding wire 23 is made of mild steel having a diameter of φ1.2, and Ar gas and CO ₂ gas are mixed. : CO ₂ = 80: 20), an increase amount WFU that is a difference obtained by subtracting the feeding speed WF1 from the feeding speed WF2 and the feeding speed WF1 (WF2 = WF1 + WFU).

  In FIG. 5, the horizontal axis represents the feeding speed WF1, and the vertical axis represents the amount of increase WFU from the feeding speed WF1 to the feeding speed WF2. For example, when the feeding speed WF1 is 4 m / min, the increase amount WFU is 1 m / min. When the feeding speed WF1 is 8 m / min, the increase amount WFU is 2 m / min. In the relationship shown in FIG. 5, the rate of increase of the feed rate WF2 with respect to the feed rate WF1, that is, the ratio of the increased amount WFU to the feed rate WF1 is about 25%. As the feeding speed WF increases, the welding current I increases, so the droplet 23d also increases. Therefore, when the feed speed WF1 increases, the increase rate of the feed speed WF2 is the same, but the increase amount WFU increases.

  The appropriate increase amount WFU (increase rate) of the feeding speed WF differs depending on the welding conditions such as the diameter and material of the welding wire 23 and the shielding gas 24G, and can be obtained in advance by, for example, confirmation of construction through experiments or the like.

  For example, when the material of the welding wire 23 is stainless steel as a different material, the stainless steel has a high viscosity and the droplet 23d is difficult to be detached. Therefore, the droplet 23d tends to be larger than the mild steel. Therefore, when the material of the welding wire 23 is stainless steel, the increase amount WFU from the feeding speed WF1 to the feeding speed WF2 is larger than that in the case of mild steel shown in FIG.

Further, as an example in which the shielding gas 24G is different, in the case of MAG welding (Ar: CO ₂ = 90: 10) using the shielding gas 24G having a large Ar gas ratio, in the case of MAG welding (Ar: CO 2 = 80: 20) There is a tendency that the droplet 23d is more easily detached and the droplet 23d is smaller. Therefore, the increase WFU in MAG welding (Ar: CO2 = 90: 10) with a large Ar gas ratio is smaller than that in the case of MAG welding (Ar: CO2 = 80: 20) shown in FIG.

  As an example in which the diameter of the wire is different, when the diameter of the welding wire 23 is larger than φ1.2, the size of the droplet 23d tends to be larger than the diameter of φ1.2. Therefore, the increase amount WFU when the diameter of the welding wire 23 is thicker than φ1.2 is larger than that when the diameter is φ1.2 shown in FIG. Conversely, when the diameter of the welding wire 23 is smaller than φ1.2, the droplet 23d tends to be smaller than when the diameter of the welding wire 23 is φ1.2. Therefore, when the diameter of the welding wire 23 is thinner than φ1.2, the increase amount WFU is smaller than when the diameter of the welding wire 23 shown in FIG. 5 is φ1.2.

  Even if the arc length H is short, the short-circuit between the welding wire 23 and the work piece 24 does not occur particularly during the peak current period IPT, and the ratio of the increase WFU to the feed speed WF1 is Basically, 10% to 30% is preferable. The correlation between the feeding speed WF1 and the increase amount WFU is not limited to the linear function shown in FIG. 5, but may be a quadratic function. The discrete values of the feeding speed WF1 and the increase amount WFU are expressed as follows. The increase amount WFU may be determined by the database to be stored.

  In normal pulse arc welding, a high current is applied in the peak current period, and the wire length is fast, so the arc length is long due to droplet formation. In the base current period, the wire length is slow due to the low current, so the arc length is long. Becomes shorter.

  Therefore, the arc length repeats long and short during one pulse period. If the arc length is too long, undercut is likely to occur during high-speed welding. Even if the arc length is shortened by lowering the voltage in order to suppress undercutting, it is inevitable that spatter at the short-circuit transition increases.

  In order to suppress sputtering, the short-circuit current may be increased from the start of the short-circuit at the time of the short-circuit until the short-circuit is opened with a predetermined slope. Thereafter, the short-circuit current may be sharply reduced to a low value by detecting a constriction immediately before opening the short-circuit. However, even this method may not be able to significantly reduce spatter.

  Therefore, in conventional pulse arc welding, it is difficult to achieve both suppression of undercutting and reduction of spatter.

  As described above, in pulse arc welding apparatus 1001 in the first embodiment, feeding speed WF of welding wire 23 in peak current period IPT is set to feeding speed WF2, and feeding speed WF is set to welding current I. By changing the feeding speeds WF1 and WF2 in synchronism with the switching between the peak current IP and the base current IB, it is possible to realize pulsed arc welding with less spatter with suppressed undercut.

  In pulse arc welding apparatus 1001 in the first embodiment, feeding speed WF of welding wire 23 is changed according to peak current period IPT and base current period IBT. In particular, in the base current period IBT, the feeding speed WF is set to the feeding speed WF1, and in the peak current period IPT, the feeding speed WF is set to be larger than the feeding speed WF1 and to the feeding speed WF2 corresponding to the feeding speed WF1. Set. Thereby, the arc length H can be made short and constant, and the molten pool can be stably made small. Further, the temperature difference between the edge of the bead and the center in the width direction of the bead becomes small, and the molten metal is hardly pulled to the center in the width direction of the bead, which is the final solidification point. Therefore, an undercut can be suppressed because the amount of the molten metal at the edge of the bead is less likely to be insufficient. The pulse arc welding apparatus 1001 according to Embodiment 1 can achieve good welding quality with suppressed undercut even during high-speed welding. In addition, the pulse arc welding apparatus 1001 in the first embodiment can suppress the spattering because the droplet 23d can be brought into the spray transition state instead of the short-circuit transition state in the peak current period IPT while suppressing the undercut. it can.

  When a short circuit occurs between the welding wire 23 and the workpiece 24, the welding current I becomes the short circuit current IS. In the welding power source device 18 shown in FIG. 1, when the short circuit control unit 11 receives a signal indicating that a short circuit has occurred from the short circuit / arc detection unit 10, the short circuit current IS is set so that the short circuit can be opened. Control.

  When the arc control unit 12 receives a signal indicating that the arc 28 is generated from the short-circuit / arc detection unit 10, a signal of a pulse current waveform based on the feed speed WF controlled by the wire feed control unit 17. Is sent to the output control unit 7 pulse waveform parameters that determine the pulse waveform of the welding current I such as the peak current IP and the base current IB. The feed speed WF is correlated with the set current or set current of the welding current I set in the welding condition setting unit 20 of the arc control unit 12. The pulse rise control unit 14 of the pulse waveform control unit 13 outputs a timing signal that starts increasing the feed speed WF from the feed speed WF1 toward the feed speed WF2 at the time t1 when the pulse rise period IPRT starts. The pulse falling control unit 16 outputs a timing signal for starting to decrease the feeding speed WF from the feeding speed WF2 toward the feeding speed WF1 at the time t3 when the pulse falling IPFT starts. The pulse waveform controller 13 controls the peak current IP and the base current IB.

  The wire feed control unit 17 of the welding power source device 18 is based on the set current of the welding current I set in the welding condition setting unit 20 provided in the robot control unit 19 and the feed speed corresponding to the set current. The WF is determined and the feeding speed WF is output. The pulse waveform control unit 13 of the arc control unit 12 receives the feed speed WF output from the wire feed control unit 17, and receives the peak current IP, the base current IB, and the pulse corresponding to the received feed speed WF. Pulse waveform parameters that determine the pulse waveform of the welding current I, such as the rising period IPRT, the peak current period IPT, and the pulse falling period IPFT, are output. Based on the signal from the wire feed control unit 17, the wire feed unit 25 including a feed roller feeds the welding wire 23.

  As described above, the pulse arc welding apparatus 1001 is configured to weld the workpiece 24 using the welding wire 23. Welding is performed while the welding current I flows through the welding wire 23 by alternately repeating a peak current period IPT in which the welding current I is the peak current IP and a base current period IBT in which the welding current I is a base current IB smaller than the peak current IP. A pulse arc welding apparatus that feeds the wire 23 toward the workpiece 24 at a feeding speed WF, generates an arc 28 between the welding wire 23 and the workpiece 24, and welds the workpiece 24. To control. The welding control unit 18b controls the feed speed WF so as to keep the arc length H of the arc 28 constant. The welding control unit 18b sets the feeding speed WF to the feeding speed WF1 in the base current period IBT, and the feeding speed WF is larger than the feeding speed WF1 and corresponds to the feeding speed WF1 in the peak current period IPT. Set to feed rate WF2.

  The feeding speed WF2 may be larger than the feeding speed WF1 by a value corresponding to at least one of the diameter and material of the welding wire 23.

  The welding control unit 18b may control the pulse arc welding apparatus 1001 so as to weld the workpiece 24 using the shield gas 24G. In this case, the feeding speed WF2 may be larger than the feeding speed WF1 by a value corresponding to at least one of the diameter and material of the welding wire 23 and the shield gas 24G.

  When the welding control unit 18b shifts from the peak current period IPT to the base current period IBT, the welding current I starts to fall from the peak current IP to the base current IB, and at the same time the feed speed WF is fed from the feed speed WF2. You may start decreasing toward WF1.

  The welding control unit 18b controls the feed speed WF so that the period until the feed speed WF2 reaches the feed speed WF2 is the same as the period until the welding current I reaches the base current IB to the peak current IP. May be. Note that the same period is a period in which not only the length but also the start time and the end time thereof are the same.

  The welding controller 18b controls the feed speed WF so that the period during which the feed speed WF reaches from the feed speed WF2 to the feed speed WF1 is the same as the period during which the welding current I reaches from the peak current to the base current IB. May be.

  The feeding speed WF2 may be larger than the feeding speed WF1 by a value in the range of 10% to 30% of the feeding speed WF1.

  As described above, in the pulse arc welding control method and the pulse arc welding apparatus 1001 according to the present embodiment, during the peak current period IPT in which the arc length H becomes longer, the feeding speed WF is larger than the feeding speed WF1 and the feeding speed is increased. The feeding speed WF2 is increased according to the feeding speed WF1. As a result, the arc length H of the peak current period IPT can be made the same as that of the base current period IBT and can be shortened so as not to be short-circuited. Accordingly, the droplet 23d is detached from the welding wire 23 in the spray transfer state without being in the short-circuit transfer state, so that the spatter due to the occurrence of the short-circuit does not occur and the spatter can be hardly generated. Thereby, the favorable welding quality which suppressed undercut at the time of high-speed welding is realizable.

(Embodiment 2)
FIG. 6 is a schematic configuration diagram of pulse arc welding apparatus 1002 in the second embodiment. In FIG. 6, the same reference numerals are assigned to the same parts as those of the pulse arc welding apparatus 1001 in the first embodiment shown in FIG. The welding control unit 18b of the pulse arc welding apparatus 1002 according to the second embodiment includes a droplet detachment detecting unit 30 that detects a point in time when the droplet 23d detaches from the welding wire 23. The droplet detachment detection unit 30 detects a constriction 23p that is formed between the droplet 23d connected to the welding wire 23 and the welding wire 23 and has a small diameter locally. Is detected.

  FIG. 7A shows the welding current I, the welding voltage V, the feeding speed WF of the welding wire 23, and the state of droplet transfer in the operation of the pulse arc welding apparatus 1002. In FIG. 7A, the same reference numerals are assigned to the same parts as those of the pulse arc welding apparatus 1001 in the first embodiment shown in FIGS. In pulse arc welding apparatus 1002 in the second embodiment, welding control unit 18b sets feeding speed WF of welding wire 23 to feeding speed WF1 in base current period IBT. The welding control unit 18b sets the feeding speed WF of the welding wire 23 to a feeding speed WF2 larger than the feeding speed WF1 during the peak current period IPT. Thereafter, at time t3 when the pulse falling period IPFT starts, the welding control unit 18b starts to decrease the feed speed WF toward the feed speed WF3 smaller than the feed speed WF1, and reaches the feed speed WF3. Thereafter, the welding control unit 18b maintains the feeding speed WF at the feeding speed WF3 and keeps the arc length H constant until the detachment of the droplet 23d from the welding wire 23 is detected.

  The welding current I, welding voltage V, droplet transfer state, and feed speed WF of the pulse arc welding apparatus 1002 shown in FIG. 7A will be described in detail. The droplet 23d begins to grow at time t1 when the pulse rising period IPRT in which the welding current I transitions from the base current IB to the peak current IP begins (state Sa). Thereafter, the droplet 23d is grown until it has an optimum size in the peak current period IPT in which the welding current I is the peak current IP (state Sb). Thereafter, a constriction state in which a constriction 23p is formed immediately before the droplet 23d is detached from the tip of the welding wire 23 in the pulse falling period IPFT in which the welding current I transitions from the peak current IP to the base current IB is realized. (State Sc). Thereafter, the droplet 23d is detached from the welding wire 23 in the base current period IBT in which the welding current I is the base current IB (state Sd).

  The control of the feeding speed WF for feeding the welding wire 23 is the main difference between the operation shown in FIG. 7A and the operation in the first embodiment shown in FIG. In the operation shown in FIG. 7A, the welding controller 18b changes the feed speed WF from the feed speed WF1 in the base current period IBT to the feed speed WF2 at the time t1 when the base current period IBT ends and the pulse rising period IPRT starts. And increase at a predetermined inclination to reach the feeding speed WF2. In the operation of the second embodiment, similarly to the operation of the first embodiment, the feed rate WF reaches the feed rate WF2 at the time t2 when the pulse rising period IPRT ends and the peak current period IPT starts. Thereafter, the welding control unit 18b changes the feed speed WF from the feed speed WF2 of the peak current period IPT to the feed speed WF1 of the base current period IBT at the time t3 when the peak current period IPT ends and the pulse falling period IPFT starts. The feed rate starts to decrease at a predetermined gradient toward the lower feed rate WF3, and is maintained at the feed rate WF3 after reaching the feed rate WF3. Thereafter, the welding controller 18b increases the feeding speed WF from the feeding speed WF3 to the feeding speed WF1 at the detachment time td when the droplet detachment detecting section 30 detects the detachment of the droplet 23d from the welding wire 23. Then, after the feed speed WF1 is reached, the feed speed WF1 is maintained.

  The operation of pulse arc welding apparatus 1002 in the second embodiment, particularly when transitioning from peak current period IPT to base current period IBT, will be described in detail below. FIG. 7B is an enlarged view of the feeding speed WF of the partial MA shown in FIG. 7A, and shows the feeding speed WF before and after the detachment time td when the detachment of the droplet 23d is detected. As shown in FIG. 7A, the welding control unit 18b starts to decrease the feed speed WF from the feed speed WF2 during the peak current period IPT toward the feed speed WF3 with a predetermined slope at time t3, as shown in FIG. 7B. As described above, after the feed speed WF3 is reached, the feed speed WF3 is maintained. In the operation in the second embodiment, while the feed speed WF is decreasing from the feed speed WF2 to the feed speed WF3, similarly to the operation in the first embodiment shown in FIG. WF is the feeding speed WF1. Thereafter, the welding control unit 18b continues to further decrease the feeding speed WF toward the feeding speed WF3 at the same predetermined inclination, reaches the feeding speed WF3 at time t41, and then maintains the feeding speed WF3. To do. Thereafter, at the separation time td when the droplet detachment detecting unit 30 detects the detachment of the droplet 23d from the welding wire 23, the welding control unit 18b starts to increase the feeding speed WF from the feeding speed WF3 to the feeding speed WF1. After reaching the feeding speed WF1, the feeding speed WF1 is maintained. Thereafter, as shown in FIG. 7A, the welding control unit 18b maintains the feed speed WF at the feed speed WF1 until the time point t1 when the base current period IBT ends.

  Thus, in the pulse arc welding control method in the second embodiment, in addition to the first embodiment described above, the feed speed WF2 larger than the feed speed WF1 is changed to the feed speed WF3 smaller than the feed speed WF1. The decreased feeding speed WF starts to be increased to a feeding speed WF1 smaller than the feeding speed WF2 at the detachment time td when the detachment of the droplet 23d is detected. Just before the droplet 23d is detached from the tip of the welding wire 23, a constriction 23p is formed between the droplet 23d connected to the welding wire 23 and the welding wire. The droplet detachment detecting unit 30 of the welding control unit 18b according to the second embodiment monitors the welding voltage V and determines the detachment time td when the droplet 23d detaches based on the detection of the formation of the constriction 23p. To do.

  By repeating this droplet transfer (detachment) state shown in FIG. 7A at a pulse frequency PHz, a stable welding state can be realized while keeping a short arc length H constant, and a bead having a beautiful appearance with less spatter without undercut. Is obtained.

  The feeding speed WF3 is smaller than the feeding speed WF1 by a value corresponding to at least one of the welding conditions including the material of the welding wire 23 and the shielding gas 24G.

FIG. 8 shows the relationship between the feeding speeds WF1 and WF3. Specifically, FIG. 8 shows a pulse MAG welding (Ar: CO ₂ = 80) using a shield gas 24G in which the welding wire 23 is made of mild steel having a diameter of φ1.2 and Ar gas and CO ₂ gas are mixed. 20) shows a relationship between a decrease amount WFD that is a difference obtained by subtracting the feeding speed WF1 from the feeding speed WF3 and the feeding speed WF1 (WF1 + WFD = WF3).

  In FIG. 8, the horizontal axis indicates the feeding speed WF1, and the vertical axis indicates the decrease amount WFD. For example, when the feeding speed WF1 is 4 m / min, the reduction amount WFD is −0.5 m / min. When the feeding speed WF1 is 8 m / min, the reduction amount WFD is −0.75 m / min.

  Depending on the material of the welding wire 23 at the time of droplet transfer (detachment), the constriction 23p may increase and the droplet 23d may extend. Based on the relationship shown in FIG. 8, the arc length H is kept constant by making the feeding speed WF smaller than the feeding speed WF1 in accordance with the elongation of the droplet 23d. Since the welding current I increases as the feeding speed WF increases, the droplet 23d and the constriction 23p tend to be longer. Therefore, the reduction amount WFD from the feed speed WF1 to the feed speed WF3 also increases.

  The appropriate reduction amount WFD varies depending on the welding conditions such as the wire material of the welding wire 23 and the shielding gas, and can be obtained, for example, by confirming the construction such as an experiment.

  For example, as an example of different materials, when the material of the welding wire 23 is stainless steel, the stainless steel has high viscosity and the droplets 23d are difficult to separate, so that the droplets 23d and the constriction 23p tend to be long. Therefore, the reduction amount WFD to the feeding speed WF3 with respect to the feeding speed WF1 tends to be larger than the reduction amount WFD when the welding wire 23 shown in FIG. 8 is made of mild steel.

In addition, as an example in which the shield gas 24G is different, in the case of MAG welding (Ar: CO ₂ = 90: 10) using the shield gas 24G having a large Ar gas ratio, the droplet 23d is easily detached, as shown in FIG. The droplet 23d and the constriction 23p tend to be shorter than the reduction amount WFD in the MAG welding using the illustrated shielding gas 24G (Ar: CO ₂ = 80: 20). Therefore, the amount of decrease WFD to the feed speed WF3 with respect to the feed speed WF1 tends to be smaller than that in the case of MAG welding (Ar: CO ₂ = 80: 20) shown in FIG.

  The relationship between the feeding speed WF1 and the decrease amount WFD may be not only a quadratic function but also a linear function, and is based on a database that stores discrete values of the feeding speed WF1 and the decrease amount WFD. The decrease amount WFD may be determined.

  In the pulse arc welding apparatus 1001 shown in FIG. 6, the droplet detachment detection unit 30 monitors the welding voltage V detected by the welding voltage detection unit 8 in real time and obtains a time differential value obtained by differentiating the welding voltage V with respect to time. . The droplet detachment detection unit 30 transmits a droplet detachment signal Cd to the wire feed control unit 17 when the time differential value of the welding voltage V exceeds a predetermined value, and the time differential value is equal to or less than the predetermined value. In some cases, the droplet separation signal Cd is not transmitted to the wire feed controller 17. The time point at which the time differential value of the welding voltage V exceeds a predetermined value is determined as the detachment time point td at which the droplet 23d detaches from the welding wire 23. The welding control unit 18b is a predetermined state indicating a state in which the constriction 23p of the droplet 23d is formed from a state in which the feed speed WF is decreased toward the feed speed WF3 from the time t3 when the pulse falling period IPFT starts. When it is detected that the time differential value of the welding voltage V exceeds this value, the feeding speed WF starts to increase from the feeding speed WF3 toward the feeding speed WF1.

  The pulse waveform control unit 13 of the pulse arc welding apparatus 1002 outputs a pulse waveform of the welding current I based on the set current set in the welding condition setting unit 20 or the feed speed WF controlled by the wire feed control unit 17. To do. The pulse rise control unit 14 of the pulse waveform control unit 13 sends the feed speed WF of the welding wire 23 in the base current period IBT at the time t1 when the pulse rise period IPRT transitioning from the base current period IBT to the peak current period IPT starts. A signal for starting to increase toward the feeding speed WF2 larger than the feeding speed WF1 is transmitted. The pulse falling control unit 16 changes the feed speed WF from the feed speed WF2 to the feed speed WF1 smaller than the feed speed WF1 at the time t3 when the pulse fall period IPFT transitioning from the peak current period IPT to the base current period IBT starts. A signal that starts to decrease toward WF3 is transmitted.

  As described above, the welding wire 23 is melted by forming the droplet 23d by flowing the welding current I through the welding wire 23, and the droplet 23d is connected to the welding wire 23. The pulse arc welding apparatus 1002 is controlled so that a constriction 23p is generated between it and 23d. When the welding control unit 18b shifts from the peak current period IPT to the base current period IBT, the welding control unit 18b changes the feed speed WF from the feed speed WF2 to the feed speed WF3 that is smaller than the feed speed WF1 and corresponds to the feed speed WF1. Decrease. When the welding control unit 18b detects that the constriction 23p has occurred, the welding control unit 18b increases the feeding speed WF from the feeding speed WF3 to the feeding speed WF1.

  The feed speed WF may be maintained at the feed speed WF1 until the base period ends after the feed speed WF is increased to the feed speed WF1 in the step of increasing the feed speed WF from the feed speed WF3 to the feed speed WF1.

  The feeding speed WF3 may be smaller than the feeding speed WF1 by a value corresponding to at least one of the material of the welding wire 23 and the shielding gas 24G.

  As described above, according to the pulse arc welding control method and the pulse arc welding apparatus 1002 in the second embodiment, the feed speed WF of the welding wire 23 is set to the base current period IBT during the peak current period IPT in which the arc length H becomes long. The feeding speed is increased to a feeding speed larger than the feeding speed WF1. In addition, depending on the material of the welding wire 23, when the constriction 23p is large at the time of droplet transfer (detachment) and the droplet 23d extends, the feed rate WF3 is smaller than the feed rate WF1 by a value corresponding to the extension. The feed speed WF is decreased, and the feed speed WF is increased to the feed speed WF1 at the separation time td when the droplet transfer (detachment detection) is detected. In this way, the welding control unit 18b adjusts the feeding speed WF of the welding wire 23 according to the welding conditions such as the material of the welding wire 23 and the shielding gas 24G. As a result, the arc length H can be kept small enough not to be short-circuited, including the peak current period IPT, similarly to the base current period IBT, and welding can be performed in a spray transition state instead of a short-circuit transition. Therefore, it is possible to substantially prevent the spatter accompanying the occurrence of a short circuit. Thus, in the pulse arc welding apparatus 1002 according to the second embodiment, the arc length H of the peak current period IPT can be shortened, and the arc length H of the peak current period IPT and the base current period IBT can be made short and constant. Good spatter reduction and good welding quality with undercut suppressed even during high-speed welding.

  With the pulse arc welding control method of the present invention, it is possible to reduce the occurrence of spatter, maintain a short arc length, realize a bead having a good appearance with suppressed undercut even at high speed welding, and continuously use a welding wire as a consumable electrode. It is useful for a pulse arc welding apparatus that performs arc welding while feeding it.

I welding current V welding voltage WF feeding speed H arc length IP peak current IB base current IBT base current period IPRT pulse rising period IPT peak current period IPFT pulse falling period PHz pulse frequency WF1 feeding speed (first feeding speed)
WF2 feed speed (second feed speed)
WF3 feed speed (third feed speed)
DESCRIPTION OF SYMBOLS 1 Input power supply 2 Primary rectification part 3 Switching element 4 Transformer 5 Secondary rectification part 6 Reactor 7 Output control part 8 Welding voltage detection part 9 Welding current detection part 10 Short circuit / arc detection part 11 Short circuit control part 12 Arc control part 13 Pulse Waveform control unit 14 Pulse rise control unit 15 Peak current control unit 16 Pulse fall control unit 17 Wire feed control unit 18 Welding power supply device 19 Robot control unit 20 Welding condition setting unit 21 Robot 22 Welding wire storage unit 23 Welding wire 24 Covered Welded object 25 Wire feeding part 26 Torch 27 Tip 28 Arc 29a Output terminal 29b Output terminal 30 Droplet separation detection part

Claims (12)

Preparing a pulse arc welding apparatus for welding a workpiece using a welding wire;
The welding wire is fed while flowing the welding current through the welding wire by alternately repeating a peak current period in which the welding current is a peak current and a base current period in which the welding current is a base current smaller than the peak current. Controlling the pulse arc welding apparatus to feed the workpiece at a speed to generate an arc between the welding wire and the workpiece and weld the workpiece;
Controlling the feed rate to keep the arc length of the arc constant;
Including
The step of controlling the feeding speed sets the feeding speed to a first feeding speed in the base current period, and makes the feeding speed larger than the first feeding speed in the peak current period and The pulse arc welding control method including the step which sets to the 2nd feeding speed according to the 1st feeding speed. 2. The pulse arc welding control method according to claim 1, wherein the second feeding speed is larger than the first feeding speed by a value corresponding to at least one of a diameter and a material of the welding wire. The step of controlling the pulse arc welding apparatus includes repeating the peak current period and the base current period alternately to flow the welding current to the welding wire and feeding the welding wire at the feeding speed. Controlling the pulsed arc welding apparatus to generate an arc between the welding wire and the workpiece and to weld the workpiece using a shielding gas. ,
2. The pulse arc welding control method according to claim 1, wherein the second feeding speed is larger than the first feeding speed by a value corresponding to at least one of a diameter and a material of the welding wire and the shield gas. The step of controlling the feeding speed includes:
At the time of transition from the base current period to the peak current period, the welding current starts to rise from the base current to the peak current, and at the same time, the feeding speed is changed from the first feeding speed to the second feeding speed. Step to start increasing,
When the welding current transitions from the peak current period to the base current period, the welding current starts to fall from the peak current to the base current, and at the same time, the feeding speed is changed from the second feeding speed to the first feeding speed. Step to begin to decrease,
The pulse arc welding control method according to any one of claims 1 to 3, further comprising: The step of controlling the feeding speed is the same as the period until the welding current reaches the peak current from the base current until the welding speed reaches the second feeding speed from the first feeding speed. The pulse arc welding control method according to any one of claims 1 to 4, further comprising a step of controlling the feeding speed as described above. The step of controlling the feeding speed is the same as the period during which the feeding speed reaches from the second feeding speed to the first feeding speed, during which the welding current reaches from the peak current to the base current. The pulse arc welding control method according to any one of claims 1 to 5, further comprising a step of controlling the feed speed so as to become. The step of controlling the pulse arc welding apparatus includes the step of flowing the welding current through the welding wire to melt the welding wire to generate droplets, and the droplets are connected to the welding wire. Controlling the pulse arc welding apparatus such that a constriction occurs between a welding wire and the droplet;
The step of controlling the feeding speed includes:
When shifting from the peak current period to the base current period, the feed speed is reduced to a third feed speed that is smaller than the first feed speed and corresponds to the first feed speed. Steps to reduce from
Increasing the feeding speed from the third feeding speed to the first feeding speed when detecting that the constriction has occurred;
The pulse arc welding control method according to any one of claims 1 to 6, further comprising: The step of controlling the feeding speed is performed by increasing the feeding speed to the first feeding speed in the step of increasing the feeding speed from the third feeding speed to the first feeding speed. The pulse arc welding control method according to claim 7, further comprising the step of maintaining the first feeding speed until the base period ends. 9. The pulse arc welding control method according to claim 7, wherein the third feeding speed is smaller than the first feeding speed by a value corresponding to at least one of a material of the welding wire and a shielding gas. The pulse arc welding control according to any one of claims 1 to 9, wherein the second feeding speed is larger than the first feeding speed by a value in a range of 10% to 30% of the first feeding speed. Method. A pulse arc welding apparatus for welding an object to be welded using a welding wire,
A wire feeding section for feeding the welding wire;
A welding power source that outputs a welding current;
A welding control unit for controlling the welding power source unit and the wire feeding unit;
With
The welding control unit
The welding wire is sent while passing the welding current through the welding wire by alternately repeating a peak current period in which the welding current is a peak current and a base current period in which the welding current is a base current smaller than the peak current. Feeding the workpiece at a feeding speed to generate an arc between the welding wire and the workpiece, and welding the workpiece;
Changing the feeding speed between the peak current period and the base current period so as to keep the arc length of the arc constant;
A pulse arc welding apparatus configured as described above. The welding control unit sets the feeding speed to the first feeding speed during the base current period and keeps the feeding speed during the peak current period so as to keep the arc length constant. The pulse arc welding apparatus according to claim 11, wherein the pulse arc welding apparatus is configured to be set to a second feeding speed that is greater than a speed and that corresponds to the first feeding speed.

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